EPAC08 - Classification:07 Accelerator Technology Main Systems/T07 Superconducting RF

07 Accelerator Technology Main Systems

T07 Superconducting RF

Paper	Title	Page
MOPP112	Status of the PEFP Superconducting RF Project	820
	S. An, Y.-S. Cho, B. H. Choi, C. Gao, Y. M. Li, Y. Z. Tang, L. Zhang KAERI, Daejon
	Superconducting RF project of the Proton Engineering Frontier Project (PEFP) aims to develop a superconducting RF linac to accelerate a proton beam above 80 MeV at 700 MHz. The preliminary design of a low-beta cryomodule has been completed. A low-beta (β=0.42) cavity, a higher-mode coupler and a fundamental power coupler (FPC) for the PEFP cavities have also been designed. A FPC baking system and high power RF conditioning system are under construction. A helium vesel made of stainless steel has been designed. A new tuner has also been designed. Two prototype copper cavities have been produced and tested. The HOM coupler has been measured on the copper cavities. A cryostat for a SRF cavity vertical testing has been designed.
MOPP113	PEFP Dumbbell Frequency and Length Tuning of a Low-beta SRF Cavity	823
	S. An, Y.-S. Cho, C. Gao, Y. M. Li, Y. Z. Tang KAERI, Daejon L. Zhang Department of Mechanics, Chang’an University, Daejon
	Based on present technology, a dumbbell fabrication is a necessary mid-process for a cavity manufacting process. A dumbbell with a right length and frequency is necessary to build up a desired cavity. In order to obtain the exact frequencies of each individual half cell of a PEFP dumbbell, a new and confirmed measurement method has been established. In this paper, the dumbbell frequency measurement method and the frequency and length tuning practices for a PEFP low-beta cavity have been described.
MOPP114	Design of the Prototypical Cryomodule for the EUROTRANS Superconducting Linac for Nuclear Waste Transmutation	826
	S. Barbanotti, N. Panzeri, P. Pierini INFN/LASA, Segrate (MI) J.-L. Biarrotte, P. Blache, C. Commeaux, P. Duthil, E. Rampnoux IPN, Orsay M. Souli GANIL, Caen
	One task of the accelerator workpackage of the EUROTRANS program for the design of a nuclear waste transmutation system is dedicated to the engineering and realization of a prototype cryomodule of the high energy section of the linac, equipped with elliptical superconducting niobium cavities. We review here the present status of the design and the planned program that foresees the experimental characterization of the fully equipped cavity and RF system under its nominal operating conditions.
MOPP115	Production and Qualification of Low Thermal Conduction Suspension Supports for the Cold Mass of Long Superconducting Acceleration Modules	829
	S. Barbanotti, M. Bonezzi, M. Todero INFN/LASA, Segrate (MI) C. Engling, K. Jensch, R. Mattusch DESY, Hamburg
	A post is an assembly of a low thermal conduction composite material pipe (fiberglass pipe) and some shrink-fit aluminum and steel discs and rings, designed to provide a mechanical support and a thermal insulation to the cold mass of the long cryomodules of the TTF, which are foreseen also for the XFEL and ILC. We review here the production, testing and qualification for the production of post supports, which have been successfully provided for the cryomodules of the TTF in DESY, the STF in KEK and ILCTA in FNAL.
MOPP117	First Test of the Cornell Single-cavity Horizontal Cryomodule	835
	S. A. Belomestnykh, E. P. Chojnacki, R. Ehrlich, R. P.K. Kaplan, M. Liepe, V. Medjidzade, D. Meidlinger, H. Padamsee, P. Quigley, J. J. Reilly, D. M. Sabol, J. Sears, V. D. Shemelin, E. N. Smith, V. Veshcherevich, D. Widger CLASSE, Ithaca
	A single-cavity horizontal test cryomodule (HTC) has been designed and fabricated recently at Cornell University for ERL project. This cryomodule is a shortened version of the full injector cryomodule, which will house five superconducting cavities. It serves as a test bench for new design features and for testing fully dressed two-cell ERL injector cavities. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high cryogenic loads from the RF cavities, input couplers, and HOM loads. The HTC was made long enough so in the future it can accommodate longer, multicell cavities of the ERL main linac. In this paper we report on results from the first full test of the HTC, including RF system and superconducting cavity performance, cryomodule studies and operation of a new 1.8 K cryogenic system.
MOPP120	Full Characterization of the Piezo Blade Tuner for Superconducting RF Cavities	838
	A. Bosotti, C. Pagani, N. Panzeri, R. Paparella INFN/LASA, Segrate (MI) C. Albrecht, K. Jensch, R. Lange, L. Lilje DESY, Hamburg J. Knobloch, O. Kugeler, A. Neumann BESSY GmbH, Berlin
	Cavity tuners are mechanical devices designed to precisely match the resonant frequency of the superconducting (SC) cavity to the RF frequency synchronous with the beam. The blade tuner is mounted coaxially to the cavity and changes the resonator frequency by varying its length. A high tuning range is desired together with small mechanical hysteresis, to allow easy and reproducible resonator setup operations. High stiffness is also demanded to the tuner system both to ensure mechanical stability and to mitigate the frequency instabilities induced by perturbations. In high gradient SC resonators, the main sources of resonant frequency instability are the Lorentz Force Detuning (LFD) under pulsed mode operation, and the microphonic noise, in continuous wave (CW) with high loaded quality factors. Piezoceramic elements add dynamic tuning capabilities to the system, allowing fast compensation of these instabilities with the help of feed-forward and feedback loops. The piezo blade tuner has been extensively tested both at room temperature and at cold once assembled on a TESLA type cavity in its final configuration. This paper presents the summary of the complete characterization tests.
MOPP121	Full Real-time Temperature Mapping System for 9-cell ILC-type Cavities	841
	A. Canabal, F. L. Krawczyk, R. J. Roybal, J. D. Sedillo, T. Tajima LANL, Los Alamos, New Mexico S. Cohen Bira, Albuquerque, New Mexico W. Haynes Fermilab, Batavia, Illinois
	The mapping of outer-wall temperatures during the vertical test of a superconducting radio-frequency (SRF) cavity has been one of the most successful tools in detecting the cavities’ critical hot spots. However, due to the excessive number of sensors needed, no fixed-type temperature mapping (T-mapping) system that covers all cells has been built for 9-cell cavities. With the consensus that T-mapping analysis is needed in order to improve the yield of high-gradient cavities, a system with a reduced data acquisition time and increased temperature sensitivity, compared to rotating-arm systems, has been developed at Los Alamos National Laboratory. The system consists of ~5,000 100 Ω 1/8W Allen-Bradley resistors placed azimuthally every 10 degrees, a similar number of other resistors and diodes that implement the switching scheme, and data acquisition codes written in Labview. The details of the system and first results are presented and discussed.
MOPP123	Design and Fabrication of the Cornell ERL Injector Cryomodule	844
	E. P. Chojnacki, S. A. Belomestnykh, Z. A. Conway, J. J. Kaufman, M. Liepe, V. Medjidzade, D. Meidlinger, H. Padamsee, P. Quigley, J. Sears, V. D. Shemelin, V. Veshcherevich CLASSE, Ithaca
	The Energy Recovery Linac (ERL) development effort at Cornell will first produce an ERL beam source. The source will consist of a DC photo-gun, a buncher cavity, beam optics, and then an SRF Injector cryomodule to accelerate the 33-100 mA cw beam from 0.3-0.5 MeV to 5-15 MeV. The Injector cryomodule is based on TTF III technology with modifications to allow cw operation and the flexibility to accommodate the wide range of beam currents, bunch lengths, and beam energy. To deliver the 0.5 MWCW average power to the beam, the Injector cryomodule will contain five SRF 2-cell cavities, each cavity having two 50 kWCW coax couplers to deliver power from 100 kWCW klystrons, of which there are five for the Injector. Both the couplers and klystrons have been tested with 30% overhead in performance. Cold beamline HOM loads are placed between each cavity and outboard of the first and last cavities. Details of the Injector cryomodule design will be presented along with insight gained from the fabrication process, which will benefit the future ERL Linac cryomodule design and proto-typing.
MOPP124	Commissioning of the 400 MHz LHC RF System	847
	E. Ciapala, L. Arnaudon, P. Baudrenghien, O. Brunner, A. Butterworth, T. P.R. Linnecar, P. Maesen, J. C. Molendijk, E. Montesinos, D. Valuch, F. Weierud CERN, Geneva
	The installation of the 400 MHz superconducting RF system in LHC is finished and commissioning is under way. The final RF system comprises four cryomodules each with four cavities in the LHC tunnel. Also underground in an adjacent cavern shielded from the main tunnel are the sixteen 300 kW klystron RF power sources with their high voltage bunkers, two Faraday cages containing RF feedback and beam control electronics, and racks containing all the slow controls. The system and the experience gained during commissioning will be described. In particular, results from conditioning the cavities and their movable main power couplers and the setting up of the low level RF feedbacks will be presented.
MOPP125	A Superconducting RF Vertical Test Facility at Daresbury Laboratory	850
	P. A. Corlett, R. Bate, C. D. Beard, B. D. Fell, P. Goudket, S. M. Pattalwar STFC/DL/ASTeC, Daresbury, Warrington, Cheshire P. K. Ambattu, G. Burt, A. C. Dexter, M. I. Tahir Cockcroft Institute, Lancaster University, Lancaster
	A superconducting RF vertical test facility (VTF) has been constructed at Daresbury Laboratory for the testing of superconducting RF cavities at 2K. When fully operational, the facility will be capable of testing a 9-cell 1.3 GHz Tesla type cavity. The facility is initially to be configured to perform phase synchronisation experiments between a pair of single cell 3.9GHz ILC crab cavities. These experiments require the cavities to operate at the same frequency; therefore a tuning mechanism has been integrated into the system. The system is described, and data from the initial operation of the facility is presented.
MOPP126	Experimental Characterization of a 700 MHz β=0.47 5 Cell Superconducting Cavity Prototype for Pulsed Proton Linac	853
	G. Devanz, J.-P. Charrier, S. Chel, Y. Gasser, P. Hardy, J. Plouin, J. P. Poupeau, D. Roudier CEA, Gif-sur-Yvette
	A 700 MHz 5 cell elliptical cavity has been developed to accelerate a high intensity proton beam in the lower energy part of a superconducting linac, starting at 80 MeV. The cavity is stiffened in order to minimize the Lorentz detuning which limits high field pulsed operation of the flatter, low beta elliptical cavities. It is equipped with a stainless steel helium vessel. The RF tests of the cavity have been carried out at 1.8 K. Cavity performance is reported in this paper. Measurements of the RF response to mechanical excitations are also presented.
MOPP127	Commissioning of Superconducting Linac at IUAC - Initial Challenges and Solutions	856
	S. Ghosh, S. Babu, J. Chacko, A. Choudhury, G. K. Chowdhury, T. S. Datta, D. Kanjilal, S. Kar, M. Kumar, A. Mandal, D. S. Mathuria, R. S. Meena, R. Mehta, K. K. Mistri, A. Pandey, P. Patra, P. N. Prakash, A. Rai, A. Roy, B. K. Sahu, S. S. Sonti, J. Zacharias IUAC, New Delhi
	During initial acceleration of ion beam through the first module of linac having eight superconducting (SC) niobium quarter wave resonators (QWR), energy gains were found to be much lower. Major problem encountered was limitation of accelerating fields in the QWR achieved at much higher RF power (up to 300 W) leading to cable melting, metal coating on SC surface and increased cryogenic losses. Cold leaks in the niobium-stainless steel transition assemblies and niobium tuner bellows also posed a major challenge. A novel way of damping mechanical vibration was implemented to reduce RF power. Cooling was improved by installing a hemispherical structure on the resonator. The drive coupler was redesigned to eliminate metal coating. Design of the tuner/transition flange assemblies was modified to avoid cold leak. After incorporation of these modifications, on-line beam acceleration through Linac was accomplished. Pulsed (1.3 ns) Silicon beam of 130 MeV from Pelletron accelerator was further bunched to 250 ps by SC Superbuncher. After acceleration through the linac module and subsequent re-bunching using SC Rebuncher, 158 MeV Silicon beam having pulse width of 400 ps was delivered.
MOPP128	Comparison of Stretched-wire, Bead-pull and Numerical Impedance Calculations on 3.9 GHz Dipole Cavities	859
	P. Goudket, C. D. Beard, P. A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire G. Burt, A. C. Dexter Cockcroft Institute, Lancaster University, Lancaster R. M. Jones Cockcroft Institute, Warrington, Cheshire
	In order to verify detailed impedance and wakefield simulations, the resonant modes in an aluminium model of the 9-cell ILC crab cavity were investigated using a stretched-wire frequency domain measurement, as well as frequency-domain bead-pull measurements. These measurements were compared to numerical simulations in order to verify that the complete cavity mode spectrum could be experimentally characterised for this high frequency structure. The analysis of the results and the accuracy and/or limitations of each method is presented.
MOPP129	Compensation of Lorentz Force Detuning for SC Linacs (with Piezo Tuners)	862
	M. K. Grecki, J. Andryszczak, T. Pozniak, K. P. Przygoda, P. M.S. Sekalski TUL-DMCS, Łódź
	The superconducting linacs use niobium cavities working with extremely high quality factor. Therefore the bandwidth of the cavity is very narrow and even subtle deformation caused by Lorentz force detunes the cavity a lot. For high gradient operation (over 15MV/m) the mechanical deformation of the cavity should be compensated by piezo tuner. The paper presents design of a piezo control system and the results of measurements of its efficiency. It was demonstrated in FLASH accelerator that an initial detuning of 300Hz can be compensated by single pulse excitation of the piezo. The described system consist of multichannel programmable pulse generator driving a 8 channel piezo amplifiers capable to supply piezos with pulses up to 1A and up to 80V. It can compensate for Lorentz force detuning in all three FLASH cryhomodules equipped with piezos (ACC3,5,6). Liepe et al. "Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner," PAC2001, pp. 1074-1076.
MOPP130	SRF Technology-Past, Present and Future Options	865
	G. Myneni, M. Hutton Jefferson Lab, Newport News, Virginia
	Superconducting radiofrequency cavities for all recent projects (CEBAF, SNS, KEKB, and TTF) have been built from high purity polycrystalline niobium with a residual resistance ratio (RRR) greater than 250. The procedures and processes used from the initial production of the high RRR polycrystalline niobium sheets to the finished cavities are complex, numerous and very expensive, and the yield of SRF cavities meeting the performance specifications is very low. CBMM – Jefferson Lab invented the large grain and single crystal niobium technologies, and the use of niobium sliced directly from the ingots is expected to change the SRF technology outlook with fewer, and more streamlined, production processes that will not only be cost effective but also generate high yield. In this paper we will show that less stringent commercial niobium specifications are required, and explore the processes and procedures that will lay the foundation for producing SRF cavities with good quality factors at high peak magnetic fields in order to make this technology friendlier for future scientific and technological applications.
MOPP131	Cryomodule Tests of the STF Baseline 9-cell Cavities at KEK	868
	E. Kako, H. Hayano, S. Noguchi, N. Ohuchi, M. Sato, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki
	The STF-Baseline superconducting cavity system, which includes four TESLA-type 9-cell cavities, input couplers and frequency tuners, has been developed for the future ILC project. A 6m-cryomodule including one of four STF-Baseline cavities was assembled for the initial test called the STF Phase -0.5. The first cool-down of the cryomodule and high power tests of the STF-Baseline cavity had been successfully carried at 2 K. The maximum accelerating gradient (Eacc,max) of 19.3 MV/m was achieved in a specific pulse width of 1.5 msec and a repetition of 5 Hz, (23.4 MV/m in a shorter pulse of 0.6 msec). The onset of x-rays radiation was observed at higher field than 15 MV/m, and the measured Qo value was about 5 x 10⁹ at 18 MV/m in accompanied with field emission. The detuning angle of about -13 degrees at 18 MV/m was successfully compensated to nearly zero by a combined operation with both an offset detuning and an optimised applied voltage in the piezo element. String assembly of four STF-Baseline cavities has been stated in Jan. 2008. The second cryomodule test for 4 cavities, called the STF Phase -1.0, is scheduled in this early summer.
MOPP132	Progress Towards Development of an L-Band SC Traveling Wave Accelerating Structure with Feedback	871
	A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio P. V. Avrakhov LPI, Moscow S. Kazakov KEK, Ibaraki N. Solyak, V. P. Yakovlev Fermilab, Batavia, Illinois
	We describe an ongoing experimental program and progress towards development of a conceptual design for a superconducting traveling wave accelerating structure for the ILC. The accelerating gradient can be significantly improved by the use of an RF feedback system redirecting the accelerating wave that passed through the superconducting traveling wave accelerator (STWA) section back to the input of the accelerating structure. The conceptual design of the SC traveling wave accelerator has been considered by P. Avrakhov et al. [PAC07, pp.2538], where shape optimization, coupler cell design and tuning issues in the feedback loop were presented. The proposed TW structure design gives an overall 24% increase in gradient over the 1 m long standing wave structure and potentially can reach 46% if a longer structure is employed. Experimental investigation of the TW SC structure considers tests of a single cavity having the same shape as the regular cell of the full-sized STWA structure, and the same ratio of the RF fields. The details of the individual parts, joint configurations along with some developments on forming and welding of the proposed cavity shapes are discussed.
MOPP135	Vertical and Horizontal Test Results of 3.9 GHz Accelerating Cavities at FNAL	874
	T. N. Khabiboulline, H. T. Edwards, M. H. Foley, E. R. Harms, A. Hocker, D. V. Mitchell, A. M. Rowe, N. Solyak Fermilab, Batavia, Illinois
	The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the electron/positron linear accelerators. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. Several 9-cell Nb cavities were tested and they did reach accelerating gradient up to 24 MV/m almost twice more than design value of 14 MV/m. Two of these cavities are with new HOM couplers with improved design. In this paper we present all results of the vertical and horizontal tests.
MOPP136	Performance of Single Crystal Niobium Cavities	877
	P. Kneisel, G. Ciovati Jefferson Lab, Newport News, Virginia A. Brinkmann, D. Reschke, W. Singer, X. Singer DESY, Hamburg
	We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystals by rolling and annealing steps; the third cavity was made by spinning. The three other cavities of the scaled LL shape (2) and TESLA shape (1) resonated at 2.3 GHz and were fabricated from “as received” single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing all cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.
MOPP137	MultiPac 2.1 - Multipacting Simulation Package with a 2D FEM Field Solver for a Microsoft Windows System	880
	Y. M. Li, S. An, Y.-S. Cho, L. Zhang KAERI, Daejon P. Ylä-Oijala Helsinki University of Technology, Helsinki
	MultiPac 2.1 is a multipacting simulation package for analyzing electron multipacting in axisymmetric RF structures with TM_0nl mode, such as RF cavities, coaxial input couplers and ceramic windows. The original package was written by P. Ylä-Oijala, and works with MATLAB 5.0 or 6.0 on Linux operating system. In order to use this code easily for Microsoft Windows customers, we have transferred the MultiPac 2.1 from the Linux system to the Microsoft Windows system. The revised MultiPac can work with Microsoft Windows MatLab 6.0 or later editions smoothly. In this paper, the installation and operation of the Windows MutiPac 2.1 have been introduced. This work was supported by the 21C Frontier R&D program in Ministry of Science and Technology of the Korean Government.
MOPP138	First Test Results from the Cornell ERL Injector Cryomodule	883
	M. Liepe, S. A. Belomestnykh, E. P. Chojnacki, Z. A. Conway, R. Ehrlich, R. P.K. Kaplan, V. Medjidzade, H. Padamsee, P. Quigley, J. J. Reilly, D. M. Sabol, J. Sears, V. D. Shemelin, E. N. Smith, V. Veshcherevich, D. Widger CLASSE, Ithaca
	Cornell University has developed and fabricated a 5 cavity SRF injector cryomodule for the acceleration of a high current (100 mA), ultra low emittance beam. This cryomodule has been installed in the Cornell ERL prototype, and is presently under extensive test. The combination of a high beam current with emittance preservation of an ultra low emittance beam results in a multitude of challenges for the SRF system, pushing parameters well beyond present state of the art. Strong HOM damping and effective HOM power extraction is required to support the 100 mA beam current. This is achieved by placing HOM beam line absorbers between all cavities. Emittance preservation is addressed by a symmetric beam line with twin input couplers, tight cavity alignment and the option of fine alignment of cold cavities. In this paper we report on first results from the injector module test, including cavity performance tests, static heat load measurements and microphonic studies.
MOPP140	Status and Test Results of High Current 5-cell SRF Cavities Developed at JLAB	886
	F. Marhauser, G. Cheng, G. Ciovati, W. A. Clemens, E. Daly, D. Forehand, J. Henry, P. Kneisel, S. Manning, R. Manus, R. A. Rimmer, C. Tennant, H. Wang Jefferson Lab, Newport News, Virginia
	A new compact CW cryomodule development for use in future ERLs and FELs is underway at JLAB. Five-cell SRF cavities have been built at 1497 MHz for moderate RF input power scenarios with waveguide endgroups to efficiently transfer the beam induced HOM energy to room temperature loads. Effort has been made as well to provide a good real-estate gradient, cryogenic efficiency and HOMs tuned to safe frequencies to minimize HOM power extracted from the beam. Preliminary tests carried out earlier for two single-cell cavities at 1497 MHz cavity -one with a waveguide endgroup- and a bare 1497 MHz five-cell cavity have exceeded gradient and Qo specifications with no signs of multipacting and encouraged us to built two fully equipped 1497 MHz five-cell cavities. We report on the latest test results and the HOM impedance budget of the cavity used to evaluate BBU limits based on special machine optics.
MOPP141	Commissioning of the ERLP SRF Systems at Daresbury Laboratory	889
	P. A. McIntosh, R. Bate, R. K. Buckley, S. R. Buckley, P. A. Corlett, A. J. Moss, J. F. Orrett, S. M. Pattalwar, A. E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire F. G. Gabriel FZD, Dresden A. R. Goulden STFC/DL/SRD, Daresbury, Warrington, Cheshire P. vom Stein ACCEL, Bergisch Gladbach
	The Energy Recovery Linac Prototype (ERLP) has been installed at Daresbury Laboratory and its baseline commissioning completed. The SRF systems for ERLP comprise two 9-cell, 1.3 GHz accelerating cavities in the injector (or Booster) cryomodule, which provide a nominal energy gain of 8 MeV for the injected 350 keV beam from the photo-injector. The beam is then accelerated in an identical two cavity cryomodule in the energy recovery main Linac, giving a final ERLP energy of 35 MeV. Each SRF accelerating cavity is powered by commercially available Inductive Output Tubes (IOTs) and the analog LLRF control system is identical to that employed on the ELBE facility at FZD Rossendorf. This paper details the commissioning experience gained for these systems and highlights the ultimate performance achieved.
MOPP144	The First Cool-down Tests of the 6 Meter-Long-Cryomodules for Superconducting RF Test Facility (STF) at KEK	892
	N. Ohuchi, F. Furuta, K. Hara, H. Hayano, N. Higashi, Y. Higashi, H. Hisamatsu, K. Hosoyama, E. Kako, Y. Kojima, M. Masuzawa, H. Matsumoto, H. Nakai, S. Noguchi, T. Saeki, K. Saito, T. Shishido, A. Terashima, N. Toge, K. Tsuchiya, K. Yokoya KEK, Ibaraki M. H. Tsai NSRRC, Hsinchu Q. J. Xu IHEP Beijing, Beijing
	KEK is presently constructing the Superconducting RF Test Facility (STF) as the center of the ILC-R&D in Asia from 2005. In this project, KEK aims to get the manufacturing and operational experiences of the RF cavity and cryomodule toward the ILC, and two cryomodules have been developed. These cryomodules are 6 meter long and have 4 nine-cell cavities in each cryostat. The basic cross section designs of the cryomodules are almost same as the design of TESLA type-III, however, each cryostat has the different type of cavities, TESLA type and Low-Loss type. The tests for the cryomodules are planed to be performed at three steps. In the first test, measurements of the cryogenic performances of these cryomodules are the main objective. One nine-cell cavity was assembled in each cryostat and the cool-down of the two cryomodules was performed. In the following tests, the four nine-cell cavities will be assembled in each cryostat as the complete integration and the beam test will be performed. In this paper, we will report the design of the cryomodules and the cryogenic performances at the first cold test.
MOPP146	The Coaxial Tuner for ILCTA_NML at Fermilab	895
	A. Bosotti, C. Pagani, N. Panzeri, R. Paparella INFN/LASA, Segrate (MI)
	The piezo Blade Tuner prototype has been successfully tested inside the horizontal cryostat, CHECHIA, at DESY and extensive tests at BESSY are planned. As suggested by the cold test results, a few minor modifications have been implemented and a set of 8 improved devices is under construction for the installation in the second module of ILCTA at Fermilab. This reviewed design, together with a simplified helium tank in prototyping, should hopefully fulfill also the XFEL requests in term of performances and cost. In particular the use of thicker blades and their slightly different distribution along the circumference produces the increase of the tuner strength and stiffness that is needed in order to fulfill the pressure vessel regulations for qualification. As in the past, two equivalent devices, respectively in titanium and stainless steel, have been designed to maintain open the possibility of the use of a SS helium vessel once the required technology were developed. The results of the extensive mechanical tests performed to validate the estimated performances and life time are also presented.
MOPP148	Design of a Magnetic Shield Internal to the Helium Vessel of SRF Cavities	898
	P. Pierini, S. Barbanotti, L. Monaco, N. Panzeri INFN/LASA, Segrate (MI)
	The TRASCO elliptical cavities for intermediate velocity protons (β=0.47) employ a coaxial cold tuner of the blade type. To meet the perfomance goals of the 700 MHz cavities in the foreseen horizontal cryostat tests, the cavities are being equipped with a magnetic shield which lies internally to the cavity helium vessel and has a simple mechanical design and assembly procedure.
MOPP149	Recent Developments of the Superconducting CH-Cavities	901
	H. Podlech, A. Bechtold, M. Busch, F. Dziuba, H. Liebermann, U. Ratzinger IAP, Frankfurt am Main
	The Crossbar-H-mode (CH)-structure which has been developed at the IAP in Frankfurt is a multi-cell drift tube structure for the efficient acceleration of low and medium energy protons and ions. The superconducting low energy CH-prototype cavity has reached gradients of up to 7 MV/m, corresponding to an effective voltage gain of 5.6 MV. This shows that high real estate gradients can be achieved in superconducting low energy multi-cell cavities. Additionally, microphonics and tuning measurements have been performed at room temperature and at 4K. Optimized cavity geometry for high power beam projects and plans for the construction of a new superconducting cavity will be presented.
MOPP152	Bunch Lengthening Harmonic System for NSLS-II	904
	J. Rose, N. A. Towne BNL, Upton, Long Island, New York
	NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. Ion clearing gaps are required to suppress ion effects on the beam. The natural bunch length of 3mm is planned to be lengthened by means of a third harmonic cavity in order to provide a margin for the Touschek limited lifetime and for instability threshold currents. The paper presents the analysis of the bunch lengthening in this dual RF system consisting of a 500MHz fundamental and 1500 MHz harmonic system in presence of strong transient beam loading. A conceptual design of a 1500MHz SCRF cavity is developed and design performance is discussed.
MOPP153	Cavity Diagnostics Using Rotating Mapping System for L-band ERL Superconducting Cavity	907
	H. Sakai, K. Shinoe ISSP/SRL, Chiba T. Furuya, T. Takahashi, K. Umemori KEK, Ibaraki M. Sawamura JAEA/ERL, Ibaraki
	We are developing the L-band superconducting cavity for Energy Recovery Linac in Japan. In order to survey the electron emission and the heating spot of the cavity inner surface in detail, cavity diagnostics with the rotating mapping system was applied for the vertical tests of our cavities. Two types of sensor, one of which is the carbon resistor and the other is the Si PIN photo diode, was equipped to detect the temperature rise and electron emission. These two sensor arrays were arranged along the cavity axis and set on the rotating mechanics with servo motor. By rotating the sensor arrays around the cavity axis, a lot of information is obtained all over the cavity surface in detail. It is preferable that the number of sensors will be reduced compared with the usual cavity mapping system by using this rotating mapping system. We have already fabricated the Nb single cell cavities which is optimised for ERL operation and then performed the vertical test of Nb ERL single cell cavities. This paper reports the results of the mapping system with Nb single cell ERL-shape cavities.
MOPP154	Study of the High Pressure Rinsing Water Jet Interactions	910
	D. Sertore, M. Fusetti, P. M. Michelato, C. Pagani INFN/LASA, Segrate (MI)
	High Pressure Rinsing (HPR) is an important step in the cleaning of Superconducting Cavities (SC). The understanding of the interaction of the high pressure water jet on the cavity wall is of primary importance for the optimization of this process for upcoming SC based projects like XFEL and ILC. In this paper, we extend our results obtained so far in different labs and present our studies on water jet interaction on oblique surfaces and the possible induced damages.
MOPP156	Fabrication and Low Power Testing of an L-band Deflecting Cavity for Emittance-exchange at ANL	916
	J. Shi, H. Chen, W.-H. Huang, C.-X. Tang, D. Tong TUB, Beijing W. Gai, C.-J. Jing, K.-J. Kim, J. G. Power ANL, Argonne, Illinois D. Li LBNL, Berkeley, California
	An L-Band RF deflecting cavity has been built at Tsinghua University for a planned transverse-to-longitudinal emittance exchange experiment at Argonne National Laboratory (ANL). The deflector is a 1.3-GHz, 3-cell cavity operated in a TM110-like mode that delivers a deflecting voltage of 3.4 MV. In this paper, we review the cavity design and present detail of the fabrication, cold testing and tuning progress. Cell radii were left undercut to account for simulation errors, which yielded a higher frequency in the first bench measurement but removed by the final tuning on the lathe. Field distribution on axis was measured using the ‘‘bead-pull'' method and tuned to balance in the 3 cells.
MOPP157	Critical Magnetic Field Determination of Superconducting Materials	919
	A. Canabal, T. Tajima LANL, Los Alamos, New Mexico V. A. Dolgashev, S. G. Tantawi SLAC, Menlo Park, California T. Yamamoto UTNL, Ibaraki
	Using a 11.4 GHz, 50-MW, <1 μs, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.
MOPP158	Conceptual Design of Automated Systems for SRF Cavity Optical Inspection and Assembly	922
	T. Tajima, A. Canabal, T. A. Harden, R. J. Roybal LANL, Los Alamos, New Mexico
	The International Linear Collider (ILC) will require ~16,000 Superconducting Radio-Frequency (SRF) cavities at an accelerating gradient of 31.5 MV/m. One of the critical issues that needs to be addressed is the insufficient yield of high-gradient cavities that meet the requirement. This paper describes the design and initial tests of a cavity inner surface optical inspection system. Combined with a full-featured 9-cell cavity temperature mapping system being developed at LANL, we hope to be able to correlate the cavity heating and the surface condition causing it.
MOPP159	Results of Vertical Tests for the KEK-ERL Single Cell Superconducting Cavities	925
	K. Umemori, T. Furuya, T. Takahashi KEK, Ibaraki H. Sakai, K. Shinoe ISSP/SRL, Chiba M. Sawamura JAEA/ERL, Ibaraki
	The development of the superconducting cavities is indispensable for realizing the 5 GeV-class energy recovery linacs. The KEK-ERL cavity had been recently designed. Its features are the optimized cell shapes and adoption of the enlarged beampipes with eccentric-fluted structures. In order to confirm our cavity design, two types of single cell cavities had been fabricated. One is a center-cell type cavity, whose aim is a validation of the cell shape, and another is an end-cell type cavity, which has complex structure such as the eccentric-fluted beampipes. After applying a series of surface treatments, we had assembled the cavities and performed vertical tests at KEK D10 area. Promising results have been obtained. In this presentation, we will present the results of vertical tests for these cavities.
MOPP161	Plasma Etching Rates and Surface Composition of Bulk Nb Treated in Ar/Cl2 Microwave Discharge	928
	M. Raskovic, S. Popovic, J. Upadhyay, L. Vuskovic ODU, Norfolk, Virginia H. L. Phillips, A-M. Valente-Feliciano Jefferson Lab, Newport News, Virginia
	To achieve theoretically predicted values of the accelerating fields in superconducting radiofrequency (SRF) cavities, their inside surface should be fairly smooth and free of impurities. Thus, surface preparation is the critical step in production of SRF cavities. Plasma etching process is a dry chemistry technique that can be used to achieve these requirements. It is based on interaction between reactive halogen species produced in the glow discharge and the surface. During this process, volatile Nb halides are evaporated from the surface of Nb, removing the mechanically damaged and contaminated layer. We present treatment of bulk Nb samples in the Ar/Cl2 microwave discharge. We achieved etching rates comparable to the rates obtained with the electropolishing method without introducing impurities in Nb. The rate dependence on various discharge parameters and reactive gas composition is presented. Surface composition and topology measurements were carried out before and after plasma treatment to determine level of impurities. Optimal experimental conditions determined on samples will applied be on single cell cavities, pursuing improvement of their RF performance.
MOPP162	Titanium Nitride Coating of RF Ceramic Windows by Reactive DC Magnetron Sputtering	931
	V. Variola, H. Jenhani, W. Kaabi, P. Lepercq LAL, Orsay G. Keppel, V. Palmieri, F. Strada INFN/LNL, Legnaro, Padova
	Alumina is a common material for RF windows. Besides its high dielectric strength, it is stable under thermal treatment and has a low out-gassing rate. Nevertheless it has a high secondary electron emission (SEE) coefficient, which leads to multipactor limiting the achievable RF power. One way to suppress the multipactor on RF windows is to coat it with a low SEE-thin TiN film. In the frame of the LAL coupler program a sputtering bench has been developed. It is equipped with two magnetrons and titanium targets. A special rotating holder was designed to allow uniform deposition on cylindrical windows. RF etching of the substrate as a pre-treatment step is allowed, in order to remove particle contamination and to increase TiN adhesion. The TiN sputtering needs the optimisation of gas and electrical parameters. XRD analysis was performed to check the film composition and stoechiometry. The results show how to control the N2 vacancy acting on the gas flow. In addiction, the coating thickness must be optimized not to cause excessive ohmic heating, so multipactor thresholds measurements were done for different coating thickness. Thickness measurments showed a good uniformity.
MOPP164	Improvements in Field Emission: A Statistical Model for Electropolished Baked Cavities	934
	J. L. Wiener, H. Padamsee Cornell University, Ithaca, New York
	A statistical model for field emission developed in 1993 has been applied to characterize the improvement in field emitter properties and field emitter occurrence due to improvements in treatment methods for 9-cell TESLA-style cavities. The improved treatments are electropolishing, high pressure rinsing and baking (120C, 48 hours). We model the Q vs. Eacc data from 24 9-cell tests and 32 1-cell tests, all conducted at TTF by DESY. The statistical model is able to successfully simulate the observed yields by applying a factor of 3 decrease in emitter density over the emitter density prevailing for treatments in 1993, which did not include high pressure rinsing. Both simulation and data show that at Eacc = 70 MV/m the yield for field emission power less than 100 watts (Q > 8x10⁹) is less than 20%. To raise this yield to 80% will require new treatments that will reduce the emitter density by another factor of 3 at least. Further comparisons of field emission behavior will be made with data for alcohol rinsed cavities.
MOPP165	FZJ Smallest SC Triple-Spoke Cavity	937
	E. Zaplatin, W. Braeutigam, M. Pap, M. Skrobucha FZJ, Jülich P. Kneisel Jefferson Lab, Newport News, Virginia
	The paper describes the design, fabrication and test results of the smallest triple-spoke cavity (resonant frequency 760 MHz, β=0.2) developed at Forschungszentrum Juelich.
MOPP166	Control System for a PEFP FPC Baking System	940
	L. Zhang, S. An, Y.-S. Cho, Y. M. Li, Y. Z. Tang KAERI, Daejon
	In order to bake PEFP Fundamental Power Couplers (FPC) before their RF conditioning, a PEFP baking system has been designed. A control system for the baking system has been completed by using the Labview 8.2 and A-B SLC-500 PLC. In this paper, the server and client communication technology based on OLE for a Process Control (OPC) and a Labview 8.2 Datalogging and Supervisory Control (DSC) Module are described. The program for the SLC-500 PLC with four I/O modules has been written. The mechanical design and control process are described.
MOPP168	Tests on the 1.3 GHz Low Loss Single-Cell RF Superconducting Large Grain Cavities of IHEP	943
	Z. G. Zong, J. Gao, M. Q. Ge, J. Gu, H. Sun, D. Wang, Q. J. Xu, J. Y. Zhai, F. C. Zhao IHEP Beijing, Beijing F. Furuta, T. Saeki, K. Saito KEK, Ibaraki L. Q. Liu Technical Institute of Physics and Chemistry, Beijing L.-Y. Xiong, L. Zhang, T. X. Zhao, Z. G. Zong TIPC, BeiJing
	To contribute to the International Linear Collider (ILC) R&D on the 1.3 GHz low loss cavities has been carried out at IHEP since 2005. Six cavities had been fabricated by the standard technology and treated by some procedures of surface treatments, such as centrifugal barrel polishing, barrel chemical polishing, annealing, high pressure rinsing and baking at in-house IHEP. Because of the shortage of liquid helium in Beijing two large grain cavities with a fine grain one were sent to KEK for vertical tests. The large grain cavities was tested and treated at KEk and finally both reached the accelerating gradients of more than 35 MV/m with the maximum of 40.27 MV/m. This paper presents the testing and results of the large grain cavities.
WEOBM03	Development of a High Resolution Camera and Observations of Superconducting Cavities	1956
	Y. Iwashita, Y. Tajima Kyoto ICR, Uji, Kyoto H. Hayano KEK, Ibaraki
	An inspection system of the interior surface of superconducting RF cavities is developed in order to study the relation between the achievable field gradient and the defects of the interior surface. The achieved resolution is about 7 microns/pixel. So far there are good correlations between locations identified by a thermometry measurements and positions of defects found by this system. The heights or depths can be also estimated by measuring wall gradients for some well-conditioned defects. The detailed system and the data obtained from the system will be described.
	Slides
THXM02	Development of the KEK-B Superconducting Crab Cavity	2927
	K. Hosoyama, K. Akai, K. Ebihara, T. Furuya, K. Hara, T. Honma, A. Kabe, Y. Kojima, S. Mitsunobu, Y. Morita, H. Nakai, K. Nakanishi, M. Ono, Y. Yamamoto KEK, Ibaraki H. Hara, K. Okubo, K. Sennyu, T. Yanagisawa MHI, Kobe
	The development of the KEK-B superconducting crab cavity, including the design, production, tests and latest parameter performances should be described in this talk.
	Slides
THPPGM01	A Control and Systems Theory Approach to the High Gradient Cavity Detuning Compensation	2952
	R. Paparella INFN/LASA, Segrate (MI)
	The compensation of dynamic detuning is of primary importance in order to operate TESLA type cavities at the high accelerating gradient foreseen for the ILC (31.5 MV/m). This article firstly resumes recent successful experiences of open loop compensation of the Lorentz force detuning, repetitive and synchronous to the RF pulse, using fast piezoelectric actuators with different fast tuning systems. Possible strategies and results for the closed loop compensation of the stochastic microphonic detuning are also presented. Lastly, a deep characterization of the system under control is given, exploiting the system transfer functions acquired through both installed piezo actuators/sensors and phase locked measurements. This ultimately allows the analytical modeling of the behavior of cavity detuning and of its active compensation with piezoelectric actuators.
	Slides